Radioactive decay can be described by the following equation in a = in ao- kt where ao is the original amount of the substance, a is the amount of the substance remaining after time t, and k is a constant that is characteristic of the substance. minutes for the radioactive isotope chromium-56, k is 1.17 x 10 if the original amount of chromium-56 in a sample is 34.5 mg, how much time is needed for the amount of chromium- 56 that remains to fall to 20.3 mg?

The amount of time needed is 4.53 minutes.

Explanation:

The equation used to calculate time period follows:

where,

= initial mass of Cr-56 isotope = 34.5 mg

A = mass of the Cr-56 isotope left after the time = 20.3 mg

t = time = ? min

k = rate constant =

Putting values in above equation, we get:

Hence, the amount of time needed is 4.53 minutes.

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e